An Investigation into the Structural Design of Polymer Thin Films: From Stimuli Responsive Polyampholyte Brushes to Polymer-Grafted Nanocomposites

Understanding how the structural design of polymer thin films impacts their response to stimuli, such as pH, is crucial for developing systems with targeted attributes to further expand the scope of their applications. These polymer systems can be modified based on the choice of monomers, composition, and structural design, which provides a tunable source for both functionality and tailorability. This tailorability in design gives rise to a wide array of molecular properties that have a significant impact on the macroscopic properties of thin films. This dissertation work aims to provide insight into how the structural design can impact properties on two categories of polymer thin films: copolymer-grafted nanocomposites and polymer brushes.Copolymer nanocomposites were investigated on how the miscibility of the copolymer-grafted nanoparticles can be tuned by using the enthalpic interactions between the graft and the polymer matrix. Changing the overall composition of the copolymer allowed us to drive dispersion of the resulting nanocomposites in the matrix. The copolymer-grafted nanoparticles were synthesized using surface-initiated activators regenerated via electron transfer atom transfer radical polymerization in which poly(methyl methacrylate-r-cyclohexyl methacrylate) was grown from the silica nanoparticle surface and dispersed in a chemically dissimilar polystyrene matrix. An investigation into how the thermomechanical properties of the resulting copolymer-grafted nanocomposites was conducted using fused deposition modeling.The second category of polymer thin films examined was polyampholyte brushes in which the impact of modifying the composition on swelling behavior was investigated. Polyampholytes are comprised of charge-positive and charge-negative repeat units, which directly contributes to trade-offs between charge which is externally regulated by solution pH and added salt, and structure. A series of swelling studies were performed to examine how copolymer composition affects structural response of random polyampholyte brushes as pH is changed and betaine, a zwitterion, is added.The work in this dissertation involves the investigation of several types of polymer thin films, the common theme is clarifying how the structural design and composition affects the properties of polymer brushes, both as copolymer-grafted nanocomposites and on planar surfaces. In total, this research provides insight into how polymer design, polymer structure, and behavior responses are associated.